By Chuck Dorcey
I had considered replacing the tailstock clamp on my Jet BD-920 lathe (which requires a wrench to adjust) with a cam-operated mechanism, but before going that route, I asked myself, “Why isn’t a quarter turn of the wrench enough to release the tailstock?”
The answer is that when the clamp under the bed is hanging loosely from the clamp bolt, it will swing and bind as soon as the tailstock starts to move. However, a rubber washer of the proper width and thickness between the clamp and the bottom of the tailstock will push the clamp away from the bed, and binding is no longer a problem. (Some form of steel spring washer could probably also be used.) Assuming that the thickness of the lathe bed is sufficiently constant, and the underside is sufficiently smooth, only a very small movement of the clamp makes the difference between a sliding fit and a fixed position.
It may be difficult to see in the photo, but from bottom to top, we have the head of the clamp bolt, the clamp, a steel flat washer, a thick rubber washer, another steel washer, the base of the tailstock, the upper part of the tailstock, and the tall nut on the clamp bolt. The steel washers protect the rubber washer from the slots in the clamp and tailstock base. The rubber washer forces the clamp to release evenly when the clamp bolt is loosened, even a quarter turn.
Now, one swing of the wrench is all I need to lock or unlock the tailstock.
